Cycloalkyl carbonyl end-capped aromatic polycarbonates

ABSTRACT

Aromatic polycarbonate chain terminated with a cyclic ester.

BACKGROUND OF THE INVENTION

The importance of chain terminating aromatic polycarbonate has beenknown for many years. Non-chain terminated aromatic polycarbonates areinsufficiently heat stable since the free phenolic end groups provide areactive site which is detrimental to the resin stability. The absenceof a chain terminating agent or condition during the preparation ofaromatic polycarbonate leads to a polymer with an overall molecularweight which frequently is so high that the polymer is too viscous tomold at reasonable temperatures.

Standard chain terminating agents employed in the preparation ofaromatic polycarbonate are members of the phenol family such as phenolitself and tert.butyl phenol. Other chain terminating agents have beendisclosed but these moieties seem to have diminished certain of thepositive characteristics of the aromatic polycarbonate. For example,German Offenlegungsschrift No. 27 16 304, laid open Oct. 19, 1978,discloses the use of a relatively long chain carboxylic acid orcarboxylic acid halide (C₉₋₂₆) in conjunction with the usual phenolicchain stopper. Athough melt viscosity is lowered thereby permittingeasier processing of the resin, a significant lowering of the heatresistance of the polymer as measured by Vicat temperature as well asembrittlement of the resin upon aging at elevated temperatures alsooccur. Improved melt viscosity (fluidity) was also obtained in JapaneseKokai No. 76 34,992 laid open Mar. 25, 1976, when capryloyl chloride wasemployed as a chain terminating agent for an aromatic polycarbonate.However the fluidity comparison was to a non-chain terminated aromaticpolycarbonate prepared under the same conditions. Reaction of thephenolic groups of non-chain terminated final polymerized polycarbonatehas been undertaken in U.S. Pat. No. 3,475,373. In this patent, finalpolymerized polycarbonate was disclosed as being treated with an acylhalide followed by a hydroxy compound to combine with the excess halide.Various alkyl and aryl acyl halides as well as chloroformates were namedas "typical acyl halides". Isopropyl chloroformate and isobutyrylchloride were included in the lists as "typical halides". Reaction ofthe end groups of the final polymer was undertaken since it was believedthat the presence of chain terminator during the preparation of thepolymer did not modify all of the characteristic hydroxyl or phenolicgroups of the polymer. The high temperature oxidative stability of thepolycarbonate polymer prepared according to the invention of the patentwas compared with the non-chain terminated polymer.

In contrast to these earlier attempts to chain terminate an aromaticpolycarbonate, the use of the cycloalkyl acyl agents of this inventionbrings about a chain terminated aromatic polycarbonate with a higherheat resistance and better impact resistance after aging at an elevatedtemperature than the use of straight alkyl acyl agents. The heatresistance and impact resistance after aging at an elevated temperatureof aromatic polycarbonate chain terminated with the cyclic agents ofthis invention is similar to or better than the aromatic polycarbonatechain terminated with a standard agent, phenol.

BRIEF SUMMARY OF THE INVENTION

In accordance with this invention there is a composition comprising anaromatic polycarbonate chain terminated with a residue having astructure of the Formula I ##STR1## wherein R is cycloalkyl of four toseven ring carbon atoms, inclusive or methyl substituted cycloalkyl offour to seven ring carbon atoms, inclusive, wherein from one to three ofthe hydrogens of the cycloalkyl group are replaced by a methyl group.

DETAILED DESCRIPTION OF THE INVENTION

Aromatic polycarbonates can be prepared by any of the usual procedures.These polymers can be prepared by reacting a dihydric phenol with acarbonate precursor in an interfacial polymerization process. Typical ofsome of the dihydric phenols that may be employed in the practice ofthis invention are 2,2-bis(4-hydroxy phenyl)propane (bisphenol-A),(2,2-bis(4-hydroxy-3-methylphenyl)propane,4,4-bis(4-hydroxyphenyl)heptane,2,2-(3,5,3',5'-tetrachloro-4,4'-dihydroxydiphenyl)propane,2,2-(3,5,3',5'tetrabromo-4,4'-dihydroxydiphenyl)propane,(3,3'-dichloro-4,4'-dihydroxyphenyl)methane, bis 4-hydroxy phenylsulfone and bis 4-hydroxy phenyl sulfide. Other dihydric phenols of thebisphenol type are also available and are disclosed in U.S. Pat. No.2,999,835; 3,028,365 and 3,334,154. Bisphenol A is preferred.

It is, of course, possible to employ two or more different dihydricphenols or a copolymer of a dihydric phenol with a glycol or withhydroxy or acid terminated polyester, or with a dibasic acid in theevent a carbonate copolymer or interpolymer rather than a homopolymer isdesired for use in the preparation of the aromatic carbonate polymers ofthis invention. Also employed in the practice of this invention may beblends of any of the above materials to provide the aromatic carbonatepolymer.

The carbonate precursor may be either a carbonyl halide, a carbonateester or a haloformate. The carbonyl halides which can be employedherein are carbonyl bromide, carbonyl chloride and mixtures thereof.Typical of the carbonate esters which may be employed herein arediphenyl carbonate, di-(halophenyl) carbonates such as di(chlorophenyl)carbonate, di-(bromophenyl) carbonate, di-(trichlorophenyl) carbonate,di-(tribromophenyl) carbonate, etc. di-(alkylphenyl) carbonate such asdi(tolyl) carbonate, etc., di-(naphthyl) carbonate, di(chloronaphthyl)carbonate, phenyl tolyl carbonate, chlorophenyl chloronaphthylcarbonate, etc., or mixtures thereof. The haloformates suitable for useherein include bis-haloformates of dihydric phenols (bis-chloroformatesof hydroquinone), or glycols (bis-haloformates of ethylene glycol,neopentyl glycol, polyethylene glycol, etc.). While other carbonateprecursors will occur to those skilled in the art, carbonyl chloride,also known as phosgene, is preferred.

Transesterification processes utilizing diphenyl carbonate are also wellknown and can be employed for the preparation of aromatic polycarbonate.

In utilizing the interfacial polymerization process, the polycarbonatepolymers of this invention are generally prepared by employing a chainterminating agent, an acid acceptor and a catalyst. A suitable acidacceptor may be either an organic or an inorganic acid acceptor. Asuitable organic acid acceptor is a tertiary amine and includes suchmaterials as pyridine, triethylamine, dimethylaniline, tributylamine,etc. The inorganic acid acceptor may be one which can be either ahydroxide, a carbonate, a bicarbonate, or a phosphate of an alkali oralkaline earth metal.

The catalysts which are employed herein can be any of the suitablecatalysts that aid the polymerization of bisphenol-A with phosgene.Suitable catalysts include tertiary amines such as, for example,triethylamine, tripropylamine, N,N-dimethylaniline, quaternary ammoniumcompounds such as, for example, tetraethyl ammonium bromide, cetyltriethyl ammonium bromide, tetra-n-heptyl-ammonium iodide,tetra-n-propyl-ammonium bromide, tetra-methyl-ammonium chloride,tetra-methyl ammonium hydroxide, tetra-n-butylammonium iodide,benzyltrimethylammonium chloride and quaternary phosphonium compoundssuch as, for example, n-butyltriphenyl phosphonium bromide andmethyltriphenyl phosphonium bromide.

The chain terminating agent functions as a molecular weight regulator inthe process of this invention. The residue previously defined in FormulaI can be derived from various agents. It is preferred to use an acidhalide or acid of the formula ##STR2## wherein X is chlorine, bromine orhydroxy and R is as previously defined in Formula I. It is preferred touse the acid chloride, X is chlorine, particularly where there is onlyfour carbon atoms. The chain terminating agent of Formula II reacts withthe OH of the bisphenol thereby making an ester bond as shown in TableI. The compound of Formula II is added to the reactor vessel so itspresence can influence the chain length as well as merely react with thephenol end group. The addition of the chain terminating agent can bemade initially, prior to the addition of the carbonate precursor orduring the addition of the carbonate precursor, and in general at anytime up to the point of reaction where the degree of polymerizationapproaches that of a high polymer. It is preferably added initially.

The quantity of chain terminating agent which can be added is aneffective amount of agent to prepare an aromatic polycarbonate having aconventional molecular weight. As mole % of diphenol employed in thereaction this quantity will vary from about 1 to about 7 mole percent,preferably 2 to about 5 mole percent.

With respect to the chain terminating agent of Formula II, thecycloalkyl of four to seven carbon atoms inclusive are cyclobutyl,cyclopentyl, cyclohexyl and cycloheptyl. Examples of methyl substitutedcycloalkyls are illustrated below: ##STR3## and the like.

Below are specific examples of the invention. These examples areintended to illustrate and not limit the inventive concept. Alsoincluded in the Tables and Preparations are comparative and controlexamples. Intrinsic viscosity (I.V.) is measured in methylene chlorideat 25° C. Melt Flow was determined according to modified ASTM D-1238.Izod impacts were obtained according to ASTM D256 and are reported inft/lbs/in. of notch. Tg as previously noted is the secondary transitiontemperature. DTUL also as previously noted is the distortion temperatureunder load obtained according to a modified ASTM D-648.

PREPARATION A Chain Terminated Bisphenol-A Polycarbonate ResinPreparation

A 1000 ml four neck flask was fitted with a mechanical stirrer, a pHprobe, aqueous caustic inlet tube and a Claisen adapter to which wasattached a dry ice condenser and a gas inlet tube. To the flask wasadded 280 ml water, 340 ml methylene chloride, 1.4 ml triethyl amine(0.01 mole) and 57 g (0.25 mole) bisphenol-A. With stirring the pH wasraised to 10 by addition of 25% aqueous sodium hydroxide, then 0.00925mole (3.7 mole%) based upon mole of BPA of the acid or acid chlorideend-capping agent was added. Phosgene was introduced into the flask at 1g/min for 30 minutes (0.3 mole) with pH maintained at 9.5 to 11.5. ThepH was adjusted to 11 at the end of the reaction. The resin layer wasseparated fron the brine layer, then washed with 3 wt. % aqueous HCluntil washing remained acidic, then twice with distilled water. Theresin was then precipitated into 1500 ml of methanol in a Waring blenderand washed with 500 ml more methanol.

Using the above procedure various chain terminated bisphenol-Apolycarbonates were prepared. The I.V. and Tg in °C. is reported foreach polycarbonate. The carbon number in parentheses refers to thenumber of carbon atoms in normal alkyl chain or cycloalkyl ring.

                  TABLE I                                                         ______________________________________                                        CHAIN        END CAP        I.V.                                              TERMINATOR   STRUCTURE      dl/g.  Tg                                         ______________________________________                                        Phenol                      .491   150.3                                      Hexanoyl chloride (C.sub.5).sup.a                                                           ##STR4##      .495   147.0                                      Cyclopentane carboxylic acid (C.sub.5)                                                      ##STR5##      .502   153.6                                      Cyclohexane carboxylic acid (C.sub.6).sup.b                                                 ##STR6##      .495   153.8                                      Octanoic acid (C.sub.7).sup.c                                                               ##STR7##      .454   144.7                                      Cycloheptane carboxylic acid (C.sub.7)                                                      ##STR8##      .478   152.9                                      ______________________________________                                         .sup.a average of two runs                                                    .sup.b cyclohexane carboxylic acid chloride and cyclohexane carboxylic        acid used as chain terminating agents at different times from above sampl     gave close I.V., .455 and .467 as well as Tg 151.6 and 151.2 respectively     .sup.c average of two runs                                               

As is observed from the data in Table I, there is a definite andsignificant upward movement in Tg when the structure of the chainterminator is varied from a straight chain alkyl to a cycloalkyl. TheTgs obtained with the cycloalkyl chain terminating agent issubstantially higher than the Tgs obtained with phenol, a standard chainterminating agent.

Preparation B Chain Terminated Bisphenol-A Polycarbonate Utilizing aLarger Reactor Vessel

To a reactor fitted with a mechanical agitator were charged 5.5 litersof deionized water, 10 liters of methylene chloride, 2280 grams (10moles) of bisphenol-A, 28 milliliters of triethylamine, 3.4 grams ofsodium gluconate, and 0.40 mole of chain terminating agent. Phosgene wasintroduced at the rate of 18 grams/minute and phosgenation is continuedfor 60 minutes. The pH was maintained at between 8.0 and 10.0 by theaddition of 25% aqueous sodium hydroxide. After phosgenation has ceased4 liters of methylene chloride were added, the brine layer separated bycentrifuge and the resin solution washed with aqueous acid water. Theresin was steam precipitated and dried. To this resin product were addedminor amounts (about 0.03 parts by weight per hundred parts by weight ofresin) of a phosphite and of an epoxy stabilizer. This resin product wasthen fed to an extruder operating at a temperature of about 500° F. toextrude the resin into strands and the extruded strands chopped intopellets. The pellets were then injection molded at about 570° F. intotest samples measuring about 21/2"×1/2"×1/8".

Using the above procedure several chain terminated bisphenol-Apolycarbonates were prepared. The I.V., Melt Flow, DTUL and aged impactstrength at an elevated temperature were reported. The superscript onthe Notched Izod values is the percent ductility. If no superscript isnoted, the samples were 100 percent ductile.

                  TABLE II                                                        ______________________________________                                                                 1/8 IN NOTCHED IZOD                                  CHAIN            DTUL    AGED AT 90° C.                                TERMINATOR I.V.   M.F.   °C.                                                                          24 hrs.                                                                             48 hrs.                                                                             96 hrs.                            ______________________________________                                        Phenol     .480   12.3   134.6 14.3   7.2.sup.40                                                                          2.7.sup.0                         Cyclohexane                                                                              .535    6.1   135.4 --    13.6.sup.80                                                                         13.6.sup.80                        carboxylic acid                                                               ______________________________________                                    

As is observed from the data in Table II, the DTUL of the cyclic chainterminating agent is significantly higher than the standard agent,phenol. Additionally, the aged impact resistance at elevatedtemperatures is significantly greater and more ductile for the cyclicagent as opposed to phenol.

What is claimed is:
 1. An aromatic polycarbonate chain terminated with aresidue having a structure of the Formula ##STR9## wherein R iscycloalkyl of four to seven ring carbon atoms, inclusive, or methylsubstituted cycloalkyl of four to seven ring carbon atoms, inclusive,wherein from one to three hydrogen atoms of the cycloalkyl group arereplaced by a methyl group.
 2. A polycarbonate in accordance with claim1 wherein R is cycloalkyl of four ring carbon atoms or methylsubstituted cyclo alkyl of four ring carbon atoms.
 3. A polycarbonate inaccordance with claim 2 wherein R is cycloalkyl of four ring carbonatoms.
 4. A polycarbonate in accordance with claim 1 wherein R iscycloalkyl of five to seven ring carbon atoms, inclusive, or methylsubstituted cycloalkyl of five to seven ring carbon atoms inclusive. 5.A polycarbonate in accordance with claim 4 wherein R is cycloalkyl offive ring carbon atoms.
 6. A polycarbonate in accordance with claim 4wherein R is cycloalkyl of six ring carbon atoms.
 7. A polycarbonate inaccordance with claim 4 wherein R is cycloalkyl of seven ring carbonatoms.
 8. A polycarbonate in accordance with claims 3, 5, 6 or 7 whereinthe aromatic polycarbonate is derived from bisphenol-A and a carbonateprecursor.